The structure of anhydrous nickel chloride in the ionic liquid 1-ethyl-3-methyl imidazolium chloride and aluminum chloride has been investigated with extended X-ray absorption fine structure (EXAFS) in both Lewis acid and Lewis base solutions. The EXAFS data of NiCl2 center dot 6H(2)O crystals were also recorded and analyzed to demonstrate the difference file technique. The difference file technique is used to obtain the structural information for the very closely spaced coordination shells of chloride and oxygen in NiCl2 center dot 6H(2)O and they are found to agree very closely with the X-ray diffraction data. The difference file technique is then used to analyze the nickel chloride in the ionic liquid solutions. Even though anhydrous NiCl2 is more soluble in the basic solution than in the acidic solution, the EXAFS data show a single coordination of four chlorides in a tetrahedron around the nickel atom in the basic solution. In a weak acid solution, there are six chlorides in a single octahedral coordination shell around the nickel. However, in a strong acid solution, in addition to the octahedral chloride-coordination shell, there is a second coordination shell of eight aluminum atoms in the form of a simple cube. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3522762] All rights reserved.